The Pentagon says Marines in Afghanistan and the crew controlling the drone in Nevada were unaware analysts watching the firefight via live video in Indiana had doubts about the targets' identity.

Reporting from Washington — A Marine and a Navy medic killed by a U.S. drone airstrike were targeted when Marine commanders in Afghanistan mistook them for Taliban fighters, even though analysts watching the Predator's video feed were uncertain whether the men were part of an enemy force.

Those are the findings of a Pentagon investigation of the first known case of friendly fire deaths involving an unmanned aircraft, the April 6 attack that killed Marine Staff Sgt. Jeremy Smith, 26, and Navy Hospitalman Benjamin D. Rast, 23.

The 381-page report, which has not been released, concludes that the Marine officers on the scene and the Air Force crew controlling the drone from half a world away were unaware that analysts watching the firefight unfold via live video at a third location had doubts about the targets' identity.

The incident closely resembles another deadly mistake involving a Predator in early 2009. In that attack, at least 15 Afghan civilians were killed after a Predator crew mistook them for a group of Taliban preparing to attack a U.S. special forces unit.

In that case, analysts located at Air Force Special Operations Command in Florida who were watching live battlefield video from the aircraft's high-altitude cameras also had doubts about the target. Their warnings that children were present were disregarded by the drone operator and by an Army captain, who authorized the airstrike.

Because names are redacted in the Pentagon report, it is unclear which Marine officer made the final decision to order the airstrike that killed Smith and Rast. But a senior Marine officer familiar with the investigation said commanders at the battalion or regimental level would have the ultimate authority, not the lieutenant who led the platoon during the battle.

The friendly fire deaths in April occurred at 8:51 a.m. in Helmand province after Smith and his platoon, members of a reserve unit from Houston, came under enemy fire. The platoon had split up while trying to clear a road near the crossroads town of Sangin, an area in which Marines were engaged in nearly daily combat with insurgents.

Smith, Rast and another Marine had separated from the others and had taken cover behind a hedgerow, where they were firing on insurgents in a cluster of nearby buildings.

Infrared cameras on the Predator overhead had picked up heat signatures of the three men and detected muzzle flashes as they fired their weapons at insurgents.

Air Force analysts who were watching the live video in Terre Haute, Indiana, noted that the gunfire appeared aimed away from the other Marines, who were behind the three. The analysts reported that gunshots were "oriented to the west, away from friendly forces," the Pentagon report says.

But the Predator pilot in Nevada and the Marine commanders on the ground "were never made aware" of the analysts' assessment.

Smith, a combat veteran on his fourth deployment, knew the airstrike was coming, but assumed the missile was aimed at a suspected Taliban position in a building 200 yards away. Smith declined to take cover in a canal with other Marines because he wanted to make sure the Predator hit the insurgent target, Pentagon officials told his father, Jerry Smith.

But the Predator crew didn't realize that Smith and the two others had separated from the other Marines, and assumed they were enemy, according to the report.

The pilot radioed "time of flight 17 seconds." A Marine at the scene suddenly radioed a warning: The missile was headed for "the wrong building." But the Hellfire exploded on Smith's position, killing him and Rast.

The analysts, who communicated with the Predator pilot via a written chat system, were never certain who Smith and Rast were. At one point, the analysts described the pair as "friendlies," but withdrew that characterization a few seconds later. They later wrote, "Unable to discern who personnel were."

Even a written assessment that the gunfire was aimed in the wrong direction was not passed along to the pilot by the Mission Intelligence Coordinator, a crew member responsible for relaying information to the pilot, the report says. The coordinator was a trainee supervised by a trainer.

The report blames the attack on a fatal mix of poor communications, faulty assumptions and "a lack of overall common situational awareness." It recommends that a Marine lieutenant and two sergeants in Smith's platoon be "formally counseled" and suggests detailed reviews of battlefield procedures, but it said no one involved in the attack was "culpably negligent or derelict in their duties."

"The chain of events … was initiated by the on-scene ground force commander's lack of overall situational awareness and inability to accurately communicate his friendly force disposition in relation to the enemy," the report said.